Share-Based Compensation - Stock Option Activity under Stock Option Plans (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
Number of Shares
Beginning balance (in shares)	906,636
Granted (in shares)	22,500
Exercised (in shares)	(11,250)
Cancelled (in shares)	(104,012)
Ending balance (in shares)	813,874
Vested and Expected to Vest at June 30, 2013 (in shares)	813,874
Exercisable at June 30, 2013 (in shares)	763,074
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 21.58
Granted (in dollars per share)	$ 16.50
Exercised (in dollars per share)	$ 7.90
Cancelled (in dollars per share)	$ 23.52
Ending balance (in dollars per share)	$ 21.46
Vested and Expected to Vest at June 30, 2013 (in dollars per share)	$ 21.46
Exercisable at June 30, 2013 (in dollars per share)	$ 21.98
Weighted Average Remaining Contractual Term
Outstanding at June 30, 2013	3 years 10 months 10 days
Vested and Expected to Vest at June 30, 2013	3 years 10 months 10 days
Exercisable at June 30, 2013	3 years 6 months 7 days
Aggregate Intrinsic Value
Outstanding at June 30, 2013	$ 1,464,190
Vested and Expected to Vest at June 30, 2013	1,464,190
Exercisable at June 30, 2013	$ 1,277,175